The production of steel and steel products, or products that incorporate steel therein, are essential to the maintenance and growth of many economies in various parts of the world. The acquisition and installation of steel refining facilities depend on a number of important considerations including environmental impact and cost efficiency. The manufacture of steel using an electric arc furnace (EAF) is a highly advantageous process in the modem steel industry because of the flexibility of the EAF in using mixes of different charge materials including liquid hot metals and the ability to produce substantially all known grades of steel.
One approach to refining steel is the use of continuous EAF charging, melting and refining systems having side feeding of the EAF, such as described in U.S. Pat. No. 4,543,124 ('124) and U.S. Pat. No. 5,800,591 ('591). The systems described in the '124 patent and the '591 patent provide continuity to the preheating of charge materials, the melting of charge materials, and the refinement of steel. Such continuous preheating, melting and refining systems incorporate furnaces having furnace heights that accommodate side feeding and off gas extraction at low gas flow velocities required to maintain suspension of dust in air. In these systems, a charging pan is located about a material entry opening in the side of the furnace. Charge material is introduced from the pan into the furnace, and CO rich off gas is transferred to the charge preheater to be used as a fuel for preheating purposes. The systems described in the '124 patent and the '591 patent are energy conservative.
Slag has been observed to accumulate beneath the pan in such systems and require removal by ramming. This causes periodic interruptions to the continuity of the refining process. What is needed is an improved method and apparatus for preheating, melting, and refining steel that extends the continuity of the overall steel production system to continuous casting by eliminating the batch operation at the ladle metallurgy station. Further needed is a method and apparatus for preheating, melting, and refining steel that permits side feeding into a furnace without requiring an increase in the furnace height and that improves the consistency of charge feeding.
Continuous steel preheating, melting and refining systems that have side feeding use equipment that interface with the furnace, such as a connecting car, is described in U.S. Pat. No. 4,681,537 and U.S. Pat. No. 4,836,732. Such equipment are prone to damage by heat and abrasion and require periodic maintenance. For example, the connecting car pan is exposed to the splash of molten steel and slag and to high temperature peaks of off gas. Consequently, the refining process may be interrupted by downtime required for the repair and maintenance of the connecting car. What is needed is a method and apparatus for preheating, melting and refining steel that facilitates the repair and maintenance of charge feeding interchangeable equipment that interface with the furnace
As previously mentioned, environmental impact and cost efficiency are important considerations prior to acquiring and installing a steel refining system as well as during actual operation. Communities and government request that industry, in general, lessen their impact on the environment. What is needed is an improved method and apparatus for preheating, melting, and refining steel that provides emission abatement without further energy consumption. In particular, what is needed is method and apparatus for preheating, melting, and refining steel, having significant reductions in electrical energy requirement, electrode consumption, manpower, impact on the environment both inside and outside of the steel plant and baghouse dust disposal.